Variable speed traction drives of the planetary type are well known. Examples are illustrated in U.S. Pat. No. 3,023,642 issued Mar. 6, 1962, 1,887,505 issued Nov. 15, 1972, 2,109,695 issued Mar. 1, 1938, and 2,836,994 issued June 3, 1958. Another form of traction drive is illustrated in U.S. Pat. No. 2,886,986 issued May 19, 1959. It would appear that the designs of the foregoing patents while generally satisfactory in certain applications would not find widespread use due to their high weight to torque transmitting ratio. Thus, the design of all of the foregoing have relatively small contact areas (or traction surfaces) between the planetary members and the traction ring which contacts the planetary members at varying radial locations to vary the output speed. This factor is primarily due to the wide variation between the diameter of the planetary members and the diameter of the traction ring which contacts the cones.
While the disadvantages set forth above would appear to be overcome in U.S. Pat. No. 1,771,807 issued July 29, 1930 it should be observed that this later design is capable of operating satisfactorily only at relatively low input speeds as it is inherently unbalanced.